The invention relates in general to a winding and tightening tool which is used for tightening a preformed coil of a self-locking retainerless dental matrix.
A winding tool of this type was introduced by the present inventor in his previous U.S. Pat. No. 3,435,905 issued Apr. 1, 1969 and entitled Tool and Method of Manufacturing the Same, hereinafter referred to as the -905 patent. This tool was improved further by the present inventor as disclosed in his U.S. Pat. No. 3,852,884 issued Dec. 10, 1974 and entitled Winding and Tightening Tool and Method of Manufacturing Same, hereinafter referred to as the -884 patent.
These tools were used to wind the preformed coil of a metal dental matrix disclosed by the inventor in his U.S. Pat. No. 3,411,214, issued Nov. 19, 1968, entitled Dental Applicance, hereinafter referred to as the -214 patent and his U.S. Pat. No. 3,921,299 issued Nov. 25, 1985 and entitled Retainerless Dental Matrix and Method of Manufacture, hereinafter referred to as the -299 patent. The -905 patent did not provide a torque limiting means, while the -884 patent provided a single torque limitor, suitable for limiting torque on a steel matrix only.
A plastic retainerless matrix was also introduced by the inventor in his U.S. Pat. No. 4,523,909 issued June 18, 1985 and entitled Plastic Dental Matrix and Method of Manufacturing Same, hereinafter referred to as the -909 patent.
To provide a tool having two separate torque limitors, one being a high torque limitor for tightening a steel matrix and another low torque limitor for tightening the plastic matrix, the present inventor disclosed a winding tool having two different torque limiting means and means for selecting the required limitor for either the metal or plastic matrix winding coil. This was disclosed in the inventor's U.S. Pat. No. 4,551,097 issued Nov. 5, 1985 and entitled Dual-Torque Winding and Tightening Tool, hereinafter referred to as the -097 patent (which patents are all incorporated here by reference).
The object of the tool torque limiting and winding tool was to provide, in a single tool, the capacity of winding the coil of the metal matrix with higher limiting torque and for winding the coil of the plastic matrix with lower limiting torque. Particularly in the case of the plastic matrix, the tearable coil could easily be damaged by exerting too much torque. With the destruction or deformation of the winding coil, the matrix could no longer be tightened and would thus not function correctly. The torque limitor of the -097 patent prevents tearing of the coil.
However, an additional problem which was not fully addressed by the -097 patent dual torque limiting and winding tool was in the tool's disability to freely disengage the winding head or member from the coil after the coil had been tightened.
It has been found that the winding head often tends to remain bound within the plastic coil when tool is reversely wound for disengagement from said coil. This makes it difficult to extricate the winding head from the coil after the matrix has been tightened. Failure to disengage is related to an undesirable "propellering" of the tool's flexible sleeve and winding head.
Referring to FIGS. 8 and 9, FIG. 8 illustrates the tendency of the winding head 42 to rotate like a propeller when the handle 21 of the winding tool is rotated reversely in the hand. When the winding head 42 of the prior tool is seated in a coil, and wound to tighten the coil this propellering motion does not occur, because the winding coil is pressed against the tooth which supports the coil against propellering. Propellering occurs only when the reverse wind is used to disengage the winding head from the coil, as the reverse winding direction draws the coil away from the tooth, losing the support which prevents propellering.
Absent said support during reverse winding for disengagement of the tool the winding head tends to move in propeller-like fashion shown in FIG. 8, causing destructive twisting of the coil without routinely effecting disengagement.
As shown in FIG. 9, it has been found that when a dentist rotates the handle 21 in an opposite direction in an attempt to remove the winding head 9 from a plastic winding coil 61, the propellering action tends to twist and deform the coil 61 out and away from the matrix 63 and away from the tooth carrying matrix. The flexible sleeve 11 which carries the winding head 9 attempts to move in propeller-like fashion as illustrated in FIG. 8. The resulting deformation of the winding coil and part of the matrix not only makes it even more difficult to remove the winding head from the winding coil but also tends to loosen the matrix 63, rendering it useless for its intended purpose.
To try to avoid this propellering action of the flexible sleeve 11 when using the tool with a plastic matrix, and during said reverse winding of the tool, dentists have been applying a finger of the hand which is not operating the winding tool and pressing this finger against the side of the winding coil 61 toward the tooth to effect an anti-propellering hold to the reversely wound coil, while the winding head is thus disengaged and removed axially from the coil. Propellering occurs only with plastic bands, as the steel matrix is stiffer and resists the propellering. This procedure is of course awkward since the dentist must reach into the patient's mouth, and position the finger over the rotating tool to reach the coil. Using the finger to hold the winding coil against propellering also obscures the dentist's field of vision, as well as cluttering the operative field. This tends to discourage the use of the finger technique, which results in the undesired deformation and destruction of the coil and matrix as illustrated in FIG. 9.
One feature of the plastic matrix was to fasten, in the coil core a staple or similar structure to act as a key-way in the core of the coil for engaging the winding head and ensuring a firm engaging connection between the winding head and the core of the coil to provide firm winding engagement of the coil. lt has been found that sometimes the staple is pushed out of correct position by inserting the winding head or else is torn out of its engagement by turning of the winding head therein, which, without said engagement, the coil was not wound and thus the matrix was not tightened on the tooth.